The compression pressure produced above the cylinder of an internal combustion engine has been measured by a compression gauge connected to the sparkplug opening in the cylinder above the piston head. After about three compression strokes of the piston, the pressure reading on the gauge will equal that normally in the cylinder and will give a good indication of the condition of the piston rings on the piston head. Various constructions of compression testers have been utilized for this purpose and have used a movable line pointer which moves over a fixed scale mounted on the device. Because of the small area of the pointer, slight changes in pointer position are not easily observed. Also, because of the smallness of the pointer, the tester had to be carefully handled to prevent damage to the pointer.